Modern wind turbines comprise a plurality of wind turbine rotor blades, typically three blades, each blade having a weight of up to 15 tons and a length of up to 55 meters or longer.
Traditionally, a blade comprises two shell parts, one defining a windward side shelf part and the other one defining a leeward side shell part. Each of the shell parts are traditionally made in one piece. To reinforce such a blade, a beam- or box-shaped, longitudinal and tubular element, i.e. a spar, can act as a reinforcing beam running lengthways, i.e. in the longitudinal direction of the blade. The spar is located in the cavity between the two wind turbine shell parts and extends substantially throughout the length of the shell cavity in order to increase the strength and stiffness of the wind turbine blade. A blade may further be reinforced by two or more spars placed lengthways side by side.
As the size of wind turbines and thus wind turbine blades are still growing, the production facilities and the transport means must be increased to handle blades of the required size. This also increases the demand on logistics and increases the associated costs.